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An optimised and proactive maintenance strategy aims to maximise the economical profit, minimise environmental impacts and keep the risk of failure to a low level. Implementation of such strategy in the context of district heating requires efforts and abilities for predicting future performances and estimating service life of district heating components. A literature review on failures (damages and performance reductions) occurring on district heating pipes, reveals that failures in district heating pipes are mainly leaks due to corrosion or mechanical impacts and reduced thermal insulation performance: leaks being the more serious damage type. A feasible service life estimation method for this type of damage is the Factor Method. Since the application of this method within the context of DH pipes has not been found in other publications, this paper focuses on describing the method and discusses the possibilities on how to apply it in two specific cases with respect to leakage: service life estimation of repaired district heating pipe sections (i.e. maintenance of district heating network) and of district heating pipes in new or extended district heating networks. A particular attention is paid on which modifying factors to consider and how to quantify them.

This paper presents the build-up and long-term performance test of a full-scale Solar-Assisted Heat Pump System (SAHPS) for residential heating in Nordic climatic conditions. This particular SAHPS was developed within the EU project ENDCHOUSING, by predominantly using components and techniques that are available on the market. The analysis primarily focuses on system performance, with emphasis on Heat Pump (HP) and total system Seasonal Performance Factor (SPF), based on long-term and full-scale operation. Analysis shows that despite unfavourable building conditions, for low energy use and utilisation of a SAHPS, the system was successfully in full operation (for about 2 years) fulfilling heating requirements. Data processing of the series representing the full year period of 2007(February)-2008(February), presented a HP and total SAHPS performance of. SPF(HP) = 2.85 and SPF(SAHPS) = 2.09. The authors argue that with an optimised SAHPS control and operation strategy, additional use of circulation pumps and energy (electricity) could be vastly reduced, hence attaining a SPF(SAHPS) value that is in parity with the SPF(HP). As the Nordic (Swedish) Endohousing SAHPS has not yet been properly optimised/designed and installed in an appropriate house, the SPFHP = 2.85 is considered satisfactory.

This paper presents the thermal modelling of an unglazed solar collector (USC) flat panel, with the aim of producing a detailed yet swift thermal steady-state model. The model is analytical, one-dimensional (ID) and derived by a fin-theory approach. It represents the thermal performance of an arbitrary duct with applied boundary conditions equal to those of a flat panel collector. The derived model is meant to be used for efficient optimisation and design of USC flat panels (or similar applications), as well as detailed thermal analysis of temperature fields and heat transfer distributions/variations at steady-state conditions; without requiring a large amount of computational power and time. Detailed surface temperatures are necessary features for durability studies of the surface coating, hence the effect of coating degradation on USC and system performance. The model accuracy and proficiency has been benchmarked against a detailed three-dimensional Finite Difference Model (3D FDM) and two simpler ID analytical models. Results from the benchmarking test show that the fin-theory model has excellent capabilities of calculating energy performances and fluid temperature profiles, as well as detailed material temperature fields and heat transfer distributions/variations (at steady-state conditions), while still being suitable for component analysis in junction to system simulations as the model is analytical. The accuracy of the model is high in comparison to the 3D FDM (the prime benchmark), as long as the fin-theory assumption prevails (no 'or negligible' temperature gradient in the fin perpendicularly to the fin length). Comparison with the other models also shows that when the USC duct material has a high thermal conductivity, the cross-sectional material temperature adopts an isothermal state (for the assessed USC duct geometry), which makes the ID isothermal model valid. When the USC duct material has a low thermal conductivity, the heat transfer course of events adopts a 1D heat flow that reassembles the conditions of the 1D simple model (for the assessed USC duct geometry); ID heat flow through the top and bottom fins/sheets as the duct wall reassembles a state of adiabatic condition.

University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Environmental engineering. KTH Royal Institute of Technology, School of Architecture and the Built Environment,, Division of Environmental Strategies Research, Department of Urban Studies, Environmental Strategies Research - fms.

Eriksson, Ola

University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Environmental engineering.

Westerberg, Ulla

University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Building engineering.

Understanding how Building Environmental Assessments Tools (BEATs) measure and define “environmental” building is of great interest to many stakeholders, but it is difficult to understand how BEATs relate to each other, as well as to make detailed and systematic tool comparisons. A framework for comparing BEATs is presented in the following which facilitates an understanding and comparison of similarities and differences in terms of structure, content, aggregation, and scope. The framework was tested by comparing three distinctly different assessment tools; LEED-NC v3, Code for Sustainable Homes (CSH), and EcoEffect. Illustrations of the hierarchical structure of the tools gave a clear overview of their structural differences. When using the framework, the analysis showed that all three tools treat issues related to the main assessment categories: Energy and Pollution, Indoor Environment, and Materials and Waste. However, the environmental issues addressed, and the parameters defining the object of study, differ and, subsequently, so do rating, results, categories, issues, input data, aggregation methodology, and weighting. This means that BEATs measure “environmental” building differently and push “environmental” design in different directions. Therefore, tool comparisons are important, and the framework can be used to make these comparisons in a more detailed and systematic way.